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按层序地层学的理论方法,研究了万安盆地B、C二个地震层序的地层沉积和岩相分布模式,并对其油气生储盖层进行了预测。 B、C二个层序分别为上新世和晚中新世沉积层,它们均由低水位体系域、海进体系域和高水位体系域组成,各体系域在沉积环境和岩相分布上具有一定的规律性。分析结果表明:C层序低水位体系域以盆底扇为主,B层序则是低水位进积楔体发育。由于物源供给不足,C层序海进体系域和高水位体系域向海方向减薄较快,以滨海平原-半深海碎屑岩沉积为主,在台地高部位发育碳酸盐岩和生物礁体,在陆架区则有高水位体系域碳酸盐岩沉积。而B层序物源供给相对充分。高水位体系域发育大型S/斜交复合型前积结构,斜坡三角洲砂泥岩沉积特别发育,陆架边缘不断向海推进。海进体系域半深海泥岩以及高水位体系域前缘三角洲泥岩均可以成为良好的烃源岩,特别是二个层序中的“生油密集段”,如果条件成熟,则是极其重要的生油岩。低水位体系域的盆底充填砂、浊积砂、进积楔砂体,海进期发育的生物礁体、海侵砂体以及高水位期三角洲前缘砂体、陆架碳酸盐岩均可能具有良好的储集性。海进体系域泥岩是理想的区域盖层。
According to the theory of sequence stratigraphy, the stratigraphic and lithofacies distribution patterns of B and C sequences in Wan’an Basin are studied, and the hydrocarbon source and reservoir caprocks are predicted. B and C are respectively the Pliocene and Late Miocene sediments, which are composed of low-water system tract, marine-derived system tract and high-water system tract. The sedimentary environment and lithofacies distribution of each system tract Has a certain regularity. The results show that the basin-bottom fan is dominant in the C-sequence low-water system tract and the B-sequence is the low-water-level wedge development. Due to the lack of provenance, the sequence stratigraphy of the C-sequence marine system tract and the highstand system tract decrease rapidly toward the seaward direction, mainly in the coastal plains-semi-deep marine clastic sediments, and the development of carbonate rocks and organisms in the upper part of the platform Reefs, in the shelf area there are high water system carbonate deposition. The source of B sequence source is relatively adequate. In the highstand system tract, a large S / skew composite foreland structure is developed. Sediments of sandstone and shale in the ramp delta develop especially, and the edge of the shelf continuously advances toward the sea. The semi-deep marine mudstones in the Haijin system and the deltaic mudstones in the front of the highstand system tract all can be good source rocks, especially the “oil-intensive sections” in the two sequences, which are extremely important if the conditions are ripe Oil rock. Sediment-filling sand, turbidite sand, progressive-wedged sand bodies, marine reefs, marine transgressive sand bodies and high -standaged delta front sand bodies and continental shelf carbonate rocks in the lowstand system tract Has good storage. The marine system tract mudstone is the ideal regional caprock.